Contents

Personal
life

Nyquist was born in the Stora Kil parish of Nilsby, Värmland, Sweden. He was the son of Lars
Jonsson Nyqvist (b. 1847) and Katrina Eriksdotter (b. 1857). His
parents had seven children: Elin Teresia, Astrid, Selma, Harry
Theodor, Aemelie, Olga Maria, and Axel. None of the seven children
were Christened. He emigrated to the USA in 1907.

Career

He worked at AT&T's Department of Development and
Research from 1917 to 1934, and continued when it became Bell Telephone Laboratories in that year,
until his retirement in 1954.

Nyquist received the IRE Medal of Honor in 1960 for
"fundamental contributions to a quantitative understanding of
thermal noise, data transmission and negative feedback." In October
1960 he was awarded the Stuart Ballantine Medal of the Franklin
Institute "for his theoretical analyses and practical
inventions in the field of communications systems during the past
forty years including, particularly, his original work in the
theories of telegraph transmission, thermal noise in electric
conductors, and in the history of feedback systems." In 1969 he was
awarded the National Academy of
Engineering's fourth Founder's Medal "in recognition of his
many fundamental contributions to engineering."

Technical contributions

As an engineer at Bell Laboratories, Nyquist did important work
on thermal noise ("Johnson–Nyquist noise"), the
stability of feedbackamplifiers, telegraphy, facsimile, television, and other
important communications problems. With Herbert E. Ives, he
helped to develop AT&T's
first facsimile machines that were made public in 1924. In 1932, he
published a classical paper on stability of feedback
amplifiers.[1] The Nyquist stability criterion
can now be found in all textbooks on feedback control theory.

His early theoretical work on determining the bandwidth
requirements for transmitting information laid the foundations for
later advances by Claude Shannon,[2] which
led to the development of information theory.

In 1927 Nyquist determined that the number of independent pulses
that could be put through a telegraph channel per unit time is
limited to twice the bandwidth of the channel.
Nyquist published his results in the paper Certain topics in
Telegraph Transmission Theory (1928). This rule is essentially
a dual of what is now known as the
Nyquist–Shannon sampling
theorem.